The present invention relates to a tire pressure detector for connection to the air pressure of the tire of a vehicle to indicate the condition of the air pressure of the tire.
The air pressure of the tires of a motor vehicle must be maintained within a limited range. Excessive high or low tire pressure may cause a traffic accident. In order to detect the air pressure of a vehicle tire, a manual tire pressure gage may be used. A regular manual tire pressure gage comprises a connector for connection to the air valve of a vehicle tire, and an indicator or LCD which indicates the pressure of air received from the vehicle tire. This structure of manual tire pressure gage can be used to measure the air pressure of the tire of a motor vehicle only when the motor vehicle is stopped. There is now a tire pressure indicator designed to be constantly attached to the air valve of the tire of a motor vehicle to automatically detect the condition of the air pressure of the tire. This structure of tire pressure indicator, as shown in FIG. 1, comprises a hollow cylindrical metal shell A, which has a top chamber A1, a bottom screw hole A2 for connection to the air valve of a vehicle tire, and an inside annular flange A3 between the top chamber A and the bottom screw hole A, a transparent top cover B covered on the metal shell A to close the top open chamber A1, the transparent top cover B having a tubular bottom coupling flange B1 fastened to the top chamber A1 of the metal shell A and an air hole B2 at the center of its top side wall, a flat plate C mounted inside the metal shell A and supported on the inside annular flange A3, the flat plate C having a plurality of air holes C1 and a bottom pin C3 for opening the air valve of the vehicle tire, a rubber flap D covered on the flat plate C and moved to close/open the air holes C1, a movable spring holder F supported on the rubber flap D, and a compression spring G mounted in the spring holder F, a display bolt H supported on the compression spring G, the display bolt H having an upper part HI and a lower part H2 respectively colored with different colors, and a rubber seal ring I mounted in the inside annular flange A3. When air is guided from the vehicle tire into the tire pressure detector, the spring holder F is moved relative to the display bolt H, and the condition of the tire pressure is visually checked. This structure of tire pressure detector is still not satisfactory in function. Because the rubber flap D wears quickly with use, tire pressure may escape out of the tire pressure detector through the gap between the rubber flap D and the flat plate C via the air hole B2 at the top cover B. The connection between the top cover B and the metal shell A cannot eliminate a friction between the top cover B and the metal shell A, and heat will be produced upon rubbing of the top cover B against the metal shell A, causing the tire pressure of the vehicle tire to be increased relatively. When the tire pressure of the vehicle tire surpasses a certain level, the top cover B will be forced away from the metal shell A. Therefore, this structure of tire pressure detector is not suitable for use in heavy-duty motor vehicles.